The present invention relates generally to a method of and apparatus for testing an optical system and, more particularly, to an improved method of and apparatus for measuring the optical properties of a cornea/intra-ocular lens system.
In the ophthalmological field, it is highly desirable to have a device which measures accurately the optical properties of a cornea and/or human eye optical lens system independent of input of the person whose eyes are being examined. This would be especially useful for pediatric and geriatric patients.
There are a number of instruments which have been proposed for testing the optical properties of patients' eyes and exemplary ones are described in U.S. Pat. Nos.: 3,536,383; 4,353,652; 4,390,255; 4,367,019; 4,367,700; 4,372,655; 4,421,391; and 4,591,247. For example, U.S. Pat. No. 3,930,732 describes an apparatus for testing the optical transfer function of a lens system which employs a laterally moving fringe pattern produced by convergence of two monochromatic coherent-radiation beams. Several components are required to be rotated or otherwise moved. For instance, U.S. Pat. No. 4,367,019 relates to an eye refractometer which includes a system for projecting a target onto the fundus of the eye. The target is rotated to determine one astigmatic axis. This allows for determination of the eye's refractive power along one axis. The target is rotated for 90.degree. to measure the refractive power along the other astigmatic axis. The foregoing group of devices, however, rely on moving components for purposes of effecting cornea and intra-ocular optical measuring functions.
It is clear that there are disadvantages associated with having high precision instruments requiring moving components. In this regard, there are significant cost and construction factors to take into account not to mention demanding calibration considerations, which must be obtained and maintained during use of such an instrument. These latter considerations are especially important given the degree of accuracy necessary for measuring the optical properties of the human eye. Beyond these considerations, however, there is also a desire to provide a measuring instrument which also reduces greatly the work and time involved in evaluating the information received, while minimizing subjective judgments of the person evaluating the information.